Fix Trac #3406 (albeit not very satisfactorily): scoped type variables
The issue here is this: type ItemColID a b = Int -- Discards a,b get :: ItemColID a b -> a -> ItemColID a b get (x :: ItemColID a b) = x :: ItemColID a b The pattern signature for 'x' doesn't actually rigidly bind a,b. This crashed GHC 6.10 with a 'readFilledBox' panic. Now we fail with an erroe message With the new outside-in algorithm we'll be able to accept this program.
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